Aerated chocolate, also known as air chocolate, is a type of chocolate which has been turned into a foam via the addition of gas bubbles. The process for manufacturing it was invented by Rowntree's in 1947. During manufacturing the fluid chocolate mass is foamed with a propellant, and then cooled in a low pressure environment. As the bubbles of gas expand they cool and help set the chocolate. This helps to maintain an even bubble distribution within the chocolate. Due to the isolating effect of the bubbles, air chocolate melts differently from compact bar chocolate — the mouthfeel is fragile-short at first, then as the chocolate is chewed it melts rapidly due to its bigger surface area. This intensifies the perception of taste.